--*- outline -*-
+* Short term
+** erroneous test
+src/complains.c changed the output of errors (prefixes), but the m4 macros
+have not been changed to reflect this change.
+Fix the message "an identifier expected" (m4) in tests/input.at.
-* URGENT: Documenting C++ output
-Write a first documentation for C++ output.
+** push-parser
+Check it too when checking the different kinds of parsers. And be
+sure to check that the initial-action is performed once per parsing.
-* Report and GLR
-How would Paul like to display the conflicted actions? In particular,
-what when two reductions are possible on a given lookahead, but one is
-part of $default. Should we make the two reductions explicit, or just
-keep $default? See the following point.
+** m4 names
+b4_shared_declarations is no longer what it is. Make it
+b4_parser_declaration for instance.
-* Report and Disabled Reductions
-See `tests/conflicts.at (Defaulted Conflicted Reduction)', and decide
-what we want to do.
+** yychar in lalr1.cc
+There is a large difference bw maint and master on the handling of
+yychar (which was removed in lalr1.cc). See what needs to be
+back-ported.
+
+
+ /* User semantic actions sometimes alter yychar, and that requires
+ that yytoken be updated with the new translation. We take the
+ approach of translating immediately before every use of yytoken.
+ One alternative is translating here after every semantic action,
+ but that translation would be missed if the semantic action
+ invokes YYABORT, YYACCEPT, or YYERROR immediately after altering
+ yychar. In the case of YYABORT or YYACCEPT, an incorrect
+ destructor might then be invoked immediately. In the case of
+ YYERROR, subsequent parser actions might lead to an incorrect
+ destructor call or verbose syntax error message before the
+ lookahead is translated. */
+
+ /* Make sure we have latest lookahead translation. See comments at
+ user semantic actions for why this is necessary. */
+ yytoken = yytranslate_ (yychar);
+
+
+** $ and others in epilogue
+A stray $ is a warning in the actions, but an error in the epilogue.
+IMHO, it should not even be a warning in the epilogue.
+
+** stack.hh
+Get rid of it. The original idea is nice, but actually it makes
+the code harder to follow, and uselessly different from the other
+skeletons.
+
+** Variable names.
+What should we name `variant' and `lex_symbol'?
+
+** Get rid of fake #lines [Bison: ...]
+Possibly as simple as checking whether the column number is nonnegative.
+
+I have seen messages like the following from GCC.
+
+<built-in>:0: fatal error: opening dependency file .deps/libltdl/argz.Tpo: No such file or directory
+
+
+** Discuss about %printer/%destroy in the case of C++.
+It would be very nice to provide the symbol classes with an operator<<
+and a destructor. Unfortunately the syntax we have chosen for
+%destroy and %printer make them hard to reuse. For instance, the user
+is invited to write something like
+
+ %printer { debug_stream() << $$; } <my_type>;
+
+which is hard to reuse elsewhere since it wants to use
+"debug_stream()" to find the stream to use. The same applies to
+%destroy: we told the user she could use the members of the Parser
+class in the printers/destructors, which is not good for an operator<<
+since it is no longer bound to a particular parser, it's just a
+(standalone symbol).
+
+** Rename LR0.cc
+as lr0.cc, why upper case?
+
+** bench several bisons.
+Enhance bench.pl with %b to run different bisons.
+
+* Various
+** YYERRCODE
+Defined to 256, but not used, not documented. Probably the token
+number for the error token, which POSIX wants to be 256, but which
+Bison might renumber if the user used number 256. Keep fix and doc?
+Throw away?
-* value_components_used
-Was defined but not used: where was it coming from? It can't be to
-check if %union is used, since the user is free to $<foo>n on her
-union, doesn't she?
+Also, why don't we output the token name of the error token in the
+output? It is explicitly skipped:
-* yyerror, yyprint interface
-It should be improved, in particular when using Bison features such as
-locations, and YYPARSE_PARAMS. For the time being, it is recommended
-to #define yyerror and yyprint to steal internal variables...
+ /* Skip error token and tokens without identifier. */
+ if (sym != errtoken && id)
-* documentation
-Explain $axiom (and maybe change its name: BTYacc names it `goal',
-byacc `$accept' probably based on AT&T Yacc, Meta `Start'...).
-Complete the glossary (item, axiom, ?). Should we also rename `$'?
-BYacc uses `$end'. `$eof' is attracting, but after all we may be
-parsing a string, a stream etc.
+Of course there are issues with name spaces, but if we disable we have
+something which seems to be more simpler and more consistent instead
+of the special case YYERRCODE.
-* Error messages
-Some are really funky. For instance
+ enum yytokentype {
+ error = 256,
+ // ...
+ };
- type clash (`%s' `%s') on default action
-is really weird. Revisit them all.
+We could (should?) also treat the case of the undef_token, which is
+numbered 257 for yylex, and 2 internal. Both appear for instance in
+toknum:
-* Report documentation
+ const unsigned short int
+ parser::yytoken_number_[] =
+ {
+ 0, 256, 257, 258, 259, 260, 261, 262, 263, 264,
+
+while here
+
+ enum yytokentype {
+ TOK_EOF = 0,
+ TOK_EQ = 258,
+
+so both 256 and 257 are "mysterious".
+
+ const char*
+ const parser::yytname_[] =
+ {
+ "\"end of command\"", "error", "$undefined", "\"=\"", "\"break\"",
+
+
+** yychar == yyempty_
+The code in yyerrlab reads:
+
+ if (yychar <= YYEOF)
+ {
+ /* Return failure if at end of input. */
+ if (yychar == YYEOF)
+ YYABORT;
+ }
+
+There are only two yychar that can be <= YYEOF: YYEMPTY and YYEOF.
+But I can't produce the situation where yychar is YYEMPTY here, is it
+really possible? The test suite does not exercise this case.
+
+This shows that it would be interesting to manage to install skeleton
+coverage analysis to the test suite.
+
+** Table definitions
+It should be very easy to factor the definition of the various tables,
+including the separation bw declaration and definition. See for
+instance b4_table_define in lalr1.cc. This way, we could even factor
+C vs. C++ definitions.
+
+* From lalr1.cc to yacc.c
+** Single stack
+Merging the three stacks in lalr1.cc simplified the code, prompted for
+other improvements and also made it faster (probably because memory
+management is performed once instead of three times). I suggest that
+we do the same in yacc.c.
+
+** yysyntax_error
+The code bw glr.c and yacc.c is really alike, we can certainly factor
+some parts.
+
+
+* Report
+
+** Figures
+Some statistics about the grammar and the parser would be useful,
+especially when asking the user to send some information about the
+grammars she is working on. We should probably also include some
+information about the variables (I'm not sure for instance we even
+specify what LR variant was used).
+
+** GLR
+How would Paul like to display the conflicted actions? In particular,
+what when two reductions are possible on a given lookahead token, but one is
+part of $default. Should we make the two reductions explicit, or just
+keep $default? See the following point.
+
+** Disabled Reductions
+See `tests/conflicts.at (Defaulted Conflicted Reduction)', and decide
+what we want to do.
+
+** Documentation
Extend with error productions. The hard part will probably be finding
the right rule so that a single state does not exhibit too many yet
undocumented ``features''. Maybe an empty action ought to be
presented too. Shall we try to make a single grammar with all these
features, or should we have several very small grammars?
-* Documentation
-Some history of Bison and some bibliography would be most welcome.
-Are there any Texinfo standards for bibliography?
+** --report=conflict-path
+Provide better assistance for understanding the conflicts by providing
+a sample text exhibiting the (LALR) ambiguity. See the paper from
+DeRemer and Penello: they already provide the algorithm.
-* Several %unions
-I think this is a pleasant (but useless currently) feature, but in the
-future, I want a means to %include other bits of grammars, and _then_
-it will be important for the various bits to define their needs in
-%union.
+** Statically check for potential ambiguities in GLR grammars. See
+<http://www.i3s.unice.fr/~schmitz/papers.html#expamb> for an approach.
-When implementing multiple-%union support, bare the following in mind:
-- when --yacc, this must be flagged as an error. Don't make it fatal
- though.
+* Extensions
-- The #line must now appear *inside* the definition of yystype.
- Something like
+** $-1
+We should find a means to provide an access to values deep in the
+stack. For instance, instead of
- {
- #line 12 "foo.y"
- int ival;
- #line 23 "foo.y"
- char *sval;
- }
+ baz: qux { $$ = $<foo>-1 + $<bar>0 + $1; }
-* --report=conflict-path
-Provide better assistance for understanding the conflicts by providing
-a sample text exhibiting the (LALR) ambiguity. See the paper from
-DeRemer and Penello: they already provide the algorithm.
+we should be able to have:
-* Coding system independence
-Paul notes:
+ foo($foo) bar($bar) baz($bar): qux($qux) { $baz = $foo + $bar + $qux; }
+
+Or something like this.
+
+** %if and the like
+It should be possible to have %if/%else/%endif. The implementation is
+not clear: should it be lexical or syntactic. Vadim Maslow thinks it
+must be in the scanner: we must not parse what is in a switched off
+part of %if. Akim Demaille thinks it should be in the parser, so as
+to avoid falling into another CPP mistake.
- Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is
- 255). It also assumes that the 8-bit character encoding is
- the same for the invocation of 'bison' as it is for the
- invocation of 'cc', but this is not necessarily true when
- people run bison on an ASCII host and then use cc on an EBCDIC
- host. I don't think these topics are worth our time
- addressing (unless we find a gung-ho volunteer for EBCDIC or
- PDP-10 ports :-) but they should probably be documented
- somewhere.
+** XML Output
+There are couple of available extensions of Bison targeting some XML
+output. Some day we should consider including them. One issue is
+that they seem to be quite orthogonal to the parsing technique, and
+seem to depend mostly on the possibility to have some code triggered
+for each reduction. As a matter of fact, such hooks could also be
+used to generate the yydebug traces. Some generic scheme probably
+exists in there.
+
+XML output for GNU Bison and gcc
+ http://www.cs.may.ie/~jpower/Research/bisonXML/
+
+XML output for GNU Bison
+ http://yaxx.sourceforge.net/
* Unit rules
Maybe we could expand unit rules, i.e., transform
- exp: arith | bool;
- arith: exp '+' exp;
- bool: exp '&' exp;
+ exp: arith | bool;
+ arith: exp '+' exp;
+ bool: exp '&' exp;
into
- exp: exp '+' exp | exp '&' exp;
+ exp: exp '+' exp | exp '&' exp;
when there are no actions. This can significantly speed up some
grammars. I can't find the papers. In particular the book `LR
`Parsing Techniques: a Practical Guide', it includes information about
this issue. Does anybody have it?
-* Stupid error messages
-An example shows it easily:
-
-src/bison/tests % ./testsuite -k calc,location,error-verbose -l
-GNU Bison 1.49a test suite test groups:
-
- NUM: FILENAME:LINE TEST-GROUP-NAME
- KEYWORDS
-
- 51: calc.at:440 Calculator --locations --yyerror-verbose
- 52: calc.at:442 Calculator --defines --locations --name-prefix=calc --verbose --yacc --yyerror-verbose
- 54: calc.at:445 Calculator --debug --defines --locations --name-prefix=calc --verbose --yacc --yyerror-verbose
-src/bison/tests % ./testsuite 51 -d
-## --------------------------- ##
-## GNU Bison 1.49a test suite. ##
-## --------------------------- ##
- 51: calc.at:440 ok
-## ---------------------------- ##
-## All 1 tests were successful. ##
-## ---------------------------- ##
-src/bison/tests % cd ./testsuite.dir/51
-tests/testsuite.dir/51 % echo "()" | ./calc
-1.2-1.3: parse error, unexpected ')', expecting error or "number" or '-' or '('
-
-* read_pipe.c
-This is not portable to DOS for instance. Implement a more portable
-scheme. Sources of inspiration include GNU diff, and Free Recode.
-
-* Memory leaks in the generator
-A round of memory leak clean ups would be most welcome. Dmalloc,
-Checker GCC, Electric Fence, or Valgrind: you chose your tool.
+
+
+* Documentation
+
+** History/Bibliography
+Some history of Bison and some bibliography would be most welcome.
+Are there any Texinfo standards for bibliography?
+
+* Coding system independence
+Paul notes:
+
+ Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is
+ 255). It also assumes that the 8-bit character encoding is
+ the same for the invocation of 'bison' as it is for the
+ invocation of 'cc', but this is not necessarily true when
+ people run bison on an ASCII host and then use cc on an EBCDIC
+ host. I don't think these topics are worth our time
+ addressing (unless we find a gung-ho volunteer for EBCDIC or
+ PDP-10 ports :-) but they should probably be documented
+ somewhere.
+
+ More importantly, Bison does not currently allow NUL bytes in
+ tokens, either via escapes (e.g., "x\0y") or via a NUL byte in
+ the source code. This should get fixed.
* --graph
-Show reductions. []
+Show reductions.
* Broken options ?
-** %no-lines [ok]
-** %no-parser []
-** %pure-parser []
-** %token-table []
-** Options which could use parse_dquoted_param ().
-Maybe transfered in lex.c.
-*** %skeleton [ok]
-*** %output []
-*** %file-prefix []
-*** %name-prefix []
-
-** Skeleton strategy. []
-Must we keep %no-parser?
- %token-table?
-*** New skeletons. []
-
-* src/print_graph.c
-Find the best graph parameters. []
-
-* doc/bison.texinfo
-** Update
-informations about ERROR_VERBOSE. []
-** Add explainations about
-skeleton muscles. []
-%skeleton. []
-
-* testsuite
-** tests/pure-parser.at []
-New tests.
-
-* input synclines
-Some users create their foo.y files, and equip them with #line. Bison
-should recognize these, and preserve them.
-
-* BTYacc
-See if we can integrate backtracking in Bison. Contact the BTYacc
-maintainers.
-
-* RR conflicts
-See if we can use precedence between rules to solve RR conflicts. See
-what POSIX says.
+** %token-table
+** Skeleton strategy
+Must we keep %token-table?
* Precedence
+
+** Partial order
It is unfortunate that there is a total order for precedence. It
makes it impossible to have modular precedence information. We should
-move to partial orders.
+move to partial orders (sounds like series/parallel orders to me).
+
+** RR conflicts
+See if we can use precedence between rules to solve RR conflicts. See
+what POSIX says.
-This will be possible with a Bison parser for the grammar, as it will
-make it much easier to extend the grammar.
* $undefined
From Hans:
Suggest: Change the name $undefined to undefined; looks better in outputs.
+
* Default Action
From Hans:
- For use with my C++ parser, I transported the "switch (yyn)" statement
a Bison option where every typed default rule is explicitly written out
(same typed ruled can of course be grouped together).
-Note: Robert Anisko handles this. He knows how to do it.
-
-* Warnings
-It would be nice to have warning support. See how Autoconf handles
-them, it is fairly well described there. It would be very nice to
-implement this in such a way that other programs could use
-lib/warnings.[ch].
-
-Don't work on this without first announcing you do, as I already have
-thought about it, and know many of the components that can be used to
-implement it.
-
* Pre and post actions.
From: Florian Krohm <florian@edamail.fishkill.ibm.com>
Subject: YYACT_EPILOGUE
I was wondering what you think about adding YYACT_PROLOGUE/EPILOGUE
to bison. If you're interested, I'll work on a patch.
-* Move to Graphviz
-Well, VCG seems really dead. Move to Graphviz instead. Also, equip
-the parser with a means to create the (visual) parse tree.
+* Better graphics
+Equip the parser with a means to create the (visual) parse tree.
+
+* Complaint submessage indentation.
+We already have an implementation that works fairly well for named
+reference messages, but it would be nice to use it consistently for all
+submessages from Bison. For example, the "previous definition"
+submessage or the list of correct values for a %define variable might
+look better with indentation.
+
+However, the current implementation makes the assumption that the
+location printed on the first line is not usually much shorter than the
+locations printed on the submessage lines that follow. That assumption
+may not hold true as often for some kinds of submessages especially if
+we ever support multiple grammar files.
+
+Here's a proposal for how a new implementation might look:
+
+ http://lists.gnu.org/archive/html/bison-patches/2009-09/msg00086.html
+
+
+Local Variables:
+mode: outline
+coding: utf-8
+End:
-----
-Copyright (C) 2001, 2002 Free Software Foundation, Inc.
+Copyright (C) 2001-2004, 2006, 2008-2012 Free Software Foundation, Inc.
-This file is part of GNU Bison.
+This file is part of Bison, the GNU Compiler Compiler.
-GNU Bison is free software; you can redistribute it and/or modify
+This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2, or (at your option)
-any later version.
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
-GNU Bison is distributed in the hope that it will be useful,
+This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
-along with Bison; see the file COPYING. If not, write to
-the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-Boston, MA 02111-1307, USA.
+along with this program. If not, see <http://www.gnu.org/licenses/>.
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